Imidazole-borane polymers



United States Patent Oflice 3,418,260 Patented Dec. 24, 1968 3,418,260IMIDAZOLE-BORANE POLYMERS Swiatoslaw Trofimenko, Chatham, Del., assignorto E. I. du Pont de Nemours and Company, Wilmington, Del.,

a corporation of Delaware No Drawing. Filed Jan. 20, 1966, Ser. No.521,812 9 Claims. (Cl. 260-2) ABSTRACT OF THE DISCLOSUREImidazole-borane polymers having a recurring unit of the formulaDESCRIPTION OF THE INVENTION This invention relates to imidazolepolymers and their preparation. More specifically, the inventionconcerns imidazole-borane polymers and their preparation.

The novel polymers of this invention are represented by the recurringstructural formula:

I R R:

Y and Z can be alike or different and are selected from the groupconsisting of hydrogen, halogen (fluorine, chlorine, bromine, oriodine), hydrocarbyl of up to 12 carbon atoms, O-hydrocarbyl of up to 12carbon atoms, and substituted hydrocarbyl and O-hydrocarbyl groups inwhich the substituents can be halogen, oxyalkyl or oxyaryl of up to 6carbon atoms. Y and Z can be combined to form the divalent groups-O-alkyl-O- and -O- aryl-O- of up to 6 carbon atoms.

R, R and R can be alike or different and are selected from the groupconsisting of hydrogen, halogen of atomic number 17-53, inclusive, alkylof up to carbon atoms, aryl of 6 through 10 carbon atoms, aralkyl of 7through 12 carbon atoms, alkoxycarbonyl of up to 8 carbon atoms,alkoxyalkyl of up to 8 carbon atoms, alkoxy of up to 8 carbon atoms,alkylcarbonyl of up to 8 carbon atoms, arylcarbonyl of up to 12 carbonatoms, alkylthio of up to 8 carbon atoms, aralkylthio of up to 12 carbonatoms, cyano, nitro, formyl or dialkylcarbamido of up to 12 carbonatoms. R and R can be joined together to form a fused benzo ring, i.e.,

Hydrocarbyl includes the groups alkyl, alkylene, and aryl; and thesubstituted hydrocarbyls include haloalkyl, haloaryl, aryloxyalkyl, andaryloxyaryl. This definition of hydrocarby also applies to-O-hydrocarby" by inserting an oxa(oxygen) atom before each group.

The foregoing Formula I sufiiciently represents the polymers of thisinvention; however, other representations can be used to denote theresonance in the structural system. For example, the resonance betweenthe dative and sigma bond can also be represented by the formulae: II R1R2 R1 R2 3|! Y N N B-N N l 3- l Z I Z R R R1 13. R1 R3 i I r i r i NN-Il5 1 N1|3 I- \I/ z \i/ z J R R or by HI R1 R2 ..N L \gy 1 J All ofthese structural representations are equivalent methods of representingthe resonance which exists in the novel polymers, and the structuredenoted by Formula I will be used herein.

The novel polymers are prepared by the process aspect of the inventionwhich comprises reacting an imidazole of the formula N NE n with aborane of the formula BXYZ wherein Y and Z are defined as above, and Xis hydrogen halogen (chlorine, bromine or iodine) or alkyl of 1 through8 carbon atoms.

The BXYZ reactant is introduced into the reaction mixture either as suchor as the compound BXYT-Q. If introduced as BXY Z, X, Y and Z aredefined as above with the proviso that when Y is hydrogen only one of Xand Z can be hydrogen. In addition when X, Y or Z are alkyl, they arepreferably branched alkyl groups.

When the compound BXYZ-Q is employed, X, Y and Z are defined as in theparagraph preceding the above paragraph, i.e., each of X, Y and Z can behydrogen. Q is defined as an electron donor. For example, Q can be atriloweralkylamine, a diloweralkylether, a diloweralkylsulfide, and thelike, or when at least one of X, Y and Z is hydrogen, Q can be anotherBXY Z group to give, e.g., B2H3,B2H2(C2H5)4, 0r thfi The process iscarried out by reacting the imidazole and the borane for a timesufiicient to complete evolution of an equivalent amount of HX. Anyratio of the two reactants may be employed, but preferably,stoichiometric amounts (a 1:1 ratio), are used.

The optimum temperature for the reaction depends on the reactivity ofthe borane, such reactivity increasing in the order x-aryl, alkyl,hydrogen, halogen, and the reactivity of the imidazole, which mainlydepends on the 3 presence of bulky substituents that hinder reactivity.Thus, the lower range of operable temperatures is about C. for the morereactive monomers, and just below the decomposition point of the polymerfor the less reactive monomers, i.e., about 300 C. The preferred rangeis 100-200 C.

A solvent is not necessary; however, it is most convenient to achievethe temperatures employed by using a solvent with a reflux temperaturewithin the desired range. The preferred solvents should be unreactivewith either of the monomers, and should dissolve the monomers as well asthe polymeric product. Such solvents include aliphatic and aromatichydrocarbons, aliphatic and aromatic halocarbons and ethers.

The reaction may be carried out in an open system at atmosphericpressure with the by-product, HX being distilled out of the system. Itis usually advantageous to measure the evolution of HX in some suitablemanner such as by titration (if HX is an acid or base) or by a wet-testmeter (a volumetric device) if HX is hydrogen or a low-boiling alkane.Alternatively, the reaction may be carried out in an autoclave atautogenous pressure with the end-point being reached upon cessation offurther pressure increase (due to evolution of HX). Pressures up to 4000p.s.i. have been attained in such reactions.

Since most of the borane reactants are either pyrophoric or sensitive toair and moisture, the reaction is preferably carried out in an inert,dry atmosphere. This is accomplished by blanketing the system with drygases such as nitrogen, argon (or other inert gases), methane or otherlow-boiling hydrocarbons or halocarbons.

The novel polymers prepared by the foregoing process have molecularweights ranging from 320 to 12,000 or more. Most have molecular weightsbetween 5,000 and 12,000. In general, they are stable to air, water andheat up to their decomposition points which range from 300 to about 450C. depending upon the particular polymer. The polymers vary from viscousliquids to transparent solids.

The following examples illustrate, but do not limit, the novel productsand process of this invention:

To a suspension of 6.8 g. (0.1 mole) of imidazole, stirred undernitrogen in 150 ml. of toluene, was added 14.8 ml. (0.106 mole) oftriethylborane. Warming occurred (35) and a clear solution was obtained.It was refluxed over 100 hrs. at which time 1.4 l. of ethane had beenevolved. The solvent was distilled out at atmospheric pressure and theresidue heated at 170l80 for 2 hrs. An additional 0.3 1. of ethane wasevolved. The residue was a clear thick syrup soluble in toluene andchloroform but not in methanol.

Analysis.Calcd. for [C- H BN C, 61.8; H, 9.57; B, 7.94; N, 20.6. Found:C, 62.8; H, 9.82; B, 8.13; N, 20.0. Inherent viscosity (25% solution inchloroform at 25): 0.31.

The N.M.R. spectrum was confirmatory with 3 peaks at 1 2.48 (singlet),3.24 (singlet) and 9.67 (singlet) in the correct 1:2: 10 ratio.

Example 2.Poly-1-diethylb orylimidazole The reaction was run as inExample 1 but using o-dichlorobenzene as solvent. After ethane ceased toevolve, volatiles were removed at 200 in vacuo. The residual polymer hadinherent viscosity (chloroform) of 0.73. Osmometrically (CHCl determinedmolecular weight was about 6200. Films with adhesive properties werepressed from this polymer.

Example 3.1-diethylboryl-2-methylimidazole tetramer (R=CH R ==R =H;X,Y,Z=C H To a nitrogen-blanketed suspension of 16.4 g. (0.2 mole)Z-methylimidazole in 250 ml. xylene was added 28.2 ml.

(0.2 mole) of triethylborane. Warming occurred and the solid dissolved.The solution was stirred and refluxed overnight. There was evolved 5 l.(100%) ethane. On cooling of the solution a solid separated. It wasfiltered, washed with toluene, hexane and air-dried. There was obtained29.8 g. (99%) of crystals. The product sublimed at 300 (1 mm.). It waspurified by recrystallization from boiling xylene, from which itcrystallized as a solvate, and dried at 200/ 1 mm. The product meltssharply at 346-347.

Analysis.Calcd. for [C H BN C, 64.0; H, 10.0; B, 7.21; N, 18.7. Found:C, 64.5; H, 10.3; B, 7.31; N, 18.9. Mol. wt. calcd. for tetramer: 600Found (ebullioscopically in benzene): 632

Example 4.-Poly-1-diethylborylbenzimidazole To a nitrogen-blanketedsuspension of 23.6 g. (0.2 mole) benzimidazole in 250 ml. xylene wasadded 28.2 ml. (0.2 mole) of triethylborane. Warming occurred and thesolid dissolved. As the solution was refluxed, ethane was slowly evolvedand a solid started precipitating. After refluxing overnight, 5.1 l. ofethane had been evolved and much more solid had precipitated. This wasfiltered, washed with toluene, hexane and air-dried. The yield ofmaterial, M.P. 415420 (dec.), was 37 g. (88%). It shows no change onheating up to 410 in air.

Analysis.Calcd. for [C H BN C, 71.0; H, 8.07; B, 5.80; N, 15.05. Found:C, 71.4; H, 8.10; B, 5.05; N, 15.1.

Example 5.Poly-1-dihydroborylbenzimidazole A mixture of 14.6 g. (0.2mole) trimethylamine borane and 23.6 g. (0.2 mole) benzimidazole wasstirred and refluxed in 250 ml. toluene. When trimethylamine andhydrogen ceased to be evolved, the solution was cooled. A solidprecipitated. It was filtered, washed with toluene, hexane and airdried. There was obtained 15.5 g. of white solid. The polymer had BHbands at 23002500 cm.- in the infrared.

Analysis.Calcd. for [C H BN C, 64.7; H, 5.39; B, 8.32; N, 21.5. Found:C, 64.5; H, 5.60; B, 8.13; N, 20.5.

Example 6.Polyl -dihydrob orylimidazole (R,R ,R ,X,Y,Z=H) andpoly-l-dichloroborylimidazole (R,R ,R =H; Y,Z=Cl) Part A.A mixture of6.8 g. (0.1 mole) imidazole and 7.3 g. (0.1 mole) trimethylamine boranewas stirred and refluxed in 150 ml. toluene. Trimethylamine wascondensed into a trap and hydrogen evolved was measured by a gas meter.Within /2 hr. the theoretical amount of H (2.5 l.) was evolved. Thesolution was filtered ot remove a small amount of solid and the filtratewas stripped yielding 5 g. (63%) of a colorless syrup. The N.M.R.spectrum of poly-l-dihydroborylimidazole was confirmatory with two peaksin 1:2 ratio at about 2.3 and 3.21- and the BH- hydrogens detectable byintegration in the 8.3-9.1-r range.

Part B.The polymer was dissolved in chloroform and chlorine was bubbledin until the yellow color persisted (hydrogen chloride was given off).The solid that precipitated was filtered, washed with methylene chlorideand air-dried. Yield 8.8 g. (94%). The polymer is unaffected by heatingto 280/l mm. The infrared spectrum shows no BH absorption.

Example 7.--Poly-1-dihydroboryl-2-methylimidazole (R=CH R ,R =H; Y,Z=H)

A mixture of 14.6 (0.2 mole) trimethylamine borane and 16.4 g. (0.2mole) 2-methylimidazole was stirred and refluxed in 250 ml. toluene.Trimethylamine (trapped in a 80 trap) and hydrogen were evolved.Evolution stopped after 4 hours. The solution was concentrated yielding8.4 g. of a solid. On heating it to 300 in vacuo, a

sublimate was obtained and the residue was a colorless, transparentpolymer.

Example 8.Poly-1-diethylboryl-2,4,S-tribromomidazole (R,R ,R =Br,Y,Z=C HTo a suspension of 29.6 g. (0.97 mole) 2,4,5-tribrornoimidazole wasadded (under nitrogen) 13.8 ml. (0.97 mole) triethylborane. The reactionmixture Was stirred and refluxed for 5 /2 hours in which time thetheoretical amount of ethane was evolved. The reaction mixture wascooled and filtered. There was obtained 8.8 g. (24%) of solid polymer.

The filtrate was stripped yielding polymer of lower molecular weight asa viscous reddish syrup.

Example 9.Poly-l-dibutylborylirnidazole A mixture of 37 g. (0.55 mole)imidazole and 91 g. (0.50 mole) tributylborane was placed in a 1.5 l.(nitrogen-flushed) autoclave along with 470 ml. xylene. The mixture wasrocked and kept at 180 until no further pressure increase was observedfor two hours. This took 11 hours. The reaction mixture was filtered andthe solid (13 g.) was identified as unreacted imidazole. The filtratewas stripped and volatiles were removed in vacuo. The flask was cooled,1 l. ethylene glycol was added and the mixture was boiled for /2 hour.The polymer became detached from the flask walls and formed a plasticcohesive mass. The mixture was cooled, the glycol was decanted and thepolymer was boiled in water for 1 hour. A taffylike white solid wasobtained. It was heated to 260 in a stream of nitrogen to remove excessvolatiles. A pale amber flexible glass was obtained. The glass wasdissolved in warm chloroform, stirred with activated carbon andfiltered. The filtrate was stripped and the solvent was removed at 190/1 mm. The resulting amber polymer was analyzed.

Analysis.-Calcd. for CHHIZBNZI C, 68.8; H, 10.9; B, 5.62; N, 14.6.Found: C, 69.5; H, 11.1; B, 5.59; N, 15.0. Mol wt. (osomometry inchloroform at 37): 7500. Thermogravimetric analysis showed a 5% weightloss at 357 C. Ditferential thermal analysis showed a glass transitiontemperature at 3 C. and an endotherm peaking at 368. The inherentviscosity (0.25 solution in chloroform at 25) was 0.54.

Example 10.Polyl-diethylborylimidazole A mixture of 74 g. (0.75 mole)triethylborane and 55 g. (0.81 mole) imidazole was heated with 450 ml.xylene in a 1.5 1. nitrogen flushed autoclave for 16 hours at which timeno further pressure increase occurred. The resulting solution wasstripped and the product was purified further by being heated in vacuo'with an infrared lamp. The molecular weight of this polymer (osmometricin CHCl at 37) was 12200; 1 inh. (0.25% solution in CHCl at 25 0.46.This flexible, transparent polymer was unaffected by being boiled inwater for 48 hours.

Example 1 1 .-Poly-ldihydroboryl-2-phenylimidazole A mixture of 14.4 g.(0.1 mole) 2-phenylimidazole and 7.3 g. (0.1 mole) trimethylamine boranewas stirred and refluxed in 150 ml. toluene until gas evolution ceased.On cooling, 7.4 g. of a solid separated. Stripping of the filtrate gaveanother 8.0 g. of solid. Total yield 15.4 g. or 99%. Both solids have BHbands in the infrared. The first fraction gave hardly any sublimate onbeing heated at 300/'1 mm. It melted-around 325, started yellowingaround 390 and decomposed around 460. -It was purified by drying at 200/1 mm. and analyzed.

Analysis.-Calcd. for C H BN C, 69.1; H, 5.77; B, 6.91; N, 17.9. Found:C, 68.9; H, 5.92; B, 7.26; N, 17.9.

Example 12 .Poly- 1-diethy1boryl-2-phenylimidazole To anitrogen-blanketed suspension of 25.5 g. (0.177 mole) 2-phenylimidazolein 250 ml. xylene .was added 25.0 ml. (0.177 mole) triethyl-borane. Thetemperature rose from 25 to 31 and the solid dissolved. Upon heating,ethane evolution commenced at about and became more brisk as thetemperature rose. At 'when about 3 l. (67%) ethane had been evolved,solid started appearing. Within an hour, the theoretical amount ofethane was evolved and much solid was present. The mixture was cooled,the solid was filtered, washed with benzene, hexane and dried. There wasobtained 33.0 g. (88%) of white solid that gradually darkens and meltsin the 310360 range. Heating in vacuo at 250-300 removes a small amountof volatile impurity and the residue melts at 335347.

Analysis.-Calcd. for C H BN C, 73.7; H, 8.02; N, 13.2. Found: C, 74.1;H, 8.19; N, 13.2.

The imidazole reactants employed in this invention are well-knowncompounds. A representative list of imidazoles which can be used in theprocess of the invention includes 2 phenyl-4-methylimidazole,2-phenyl-4-phenylimidazole, diethyl imidazole-4,5-dicarboxylate,2,4,5-triphenylimidazole, 2-ethylimidazole, 4-methylimidazole, 2,- 4dimethylimidazole, 4,5 dimethylimidazole, 2,4,5-trimethylimidazole,2-benzylimidazole, 4-phenylimidazole, 4- methyl 5 phenylimidazole,4,5-diphenylimidazole, 4- methyl 2-styrylimidazole, 2-bromoimidazole,4-bromoimidazole, 2,4-dibromoimidazole, 4.5-dibromoirnidazole,2,4,5-tribromoimidazole, 2,4,5-triiodoimidazole, 4-bromo- 5phenylimidazole, 2,4-dibromo-5-phenylimidazo1e, 4- nitroimidazole, 4nitro 2-methylimidazole, 4-nitro-5- methylimidazole, 2methylthioimidazole, 2-benzylthioimidazole, 4 chloromethylimidazole,imidazole 4-carboxaldehyde, 5 methylimidazole-4-carboxaldehyde, 5-methyl 2phenylimidazole-4carboxaldehyde, 2-acetylimidazole, 5acetyl-2-methylimidazole, Z-benzoylimidazole, 2benzoyl-4-phenylimidazole, 2-benzyl-4-carbomethoxyimidazole,2-dodecylimidazole, 4-(or 5-) ethoxymethylimidazole,2-ethylthioimidazole, 2-pentadecylimidazole, 4 (or 5-)methoxyimidazole,imidazole-4,5-dicarbonitrile, 2 methylimidazole-4,S-dicarbonitrile andimidazo1e-4,5-bis N-methylcar-boxamide) Preferred imidazoles are thosein which R, R and R are hydrogen, alkyl of 1 through 6 carbon atoins,aryl of 6 through 10 carbon atoms (phenyl is most preferred), andhalogen (chlorine, bromine or iodine).

The borane reactants are also well-known compounds. Representativeboranes and borane complexes which can be used in the process of theinvention include diborane, tetrahydrofuran borane, pyridine borane,butoxydichloroborane, methoxydichloroborane, ethoxydichloroborane, 2-chloroethoxydichloroborane, 3 chloropropoxydichloroborane,4-chlorobutoxydichloroborane, allyloxydichloroborane,but-3-en-l-yloxydichloroborane, 2-methylallyloxydichloroborane,dimethoxychloroborane, diethoxychloroborane, dibutoxychloroborane, bis(2chlor0ethoxy)- chloroborane, bis(3-ch1oropropoxy)chloroborane, bis(4-chlorobutoxy)chloroborane, diallyloxychloroborane, bis-(but-2-en-1-yl-oxy) chloroborane, bis( l-methylallyloxy chloroborane,bis(Z-methylallyloxy)chloroborane, ethylenedioxychloroborane,diphenoxychloroborane, phenoxydichloroborane,o-phenylenedioxychloroborane, pmethoxyphenyldichloroborane,dibutoxybromoborane, boron trifluoride, boron tribromide, borontriiodide, phenyldibromoborane, p-phenyloxyphenyldibromoborane,n-butyldichloroborane, a-naphthyldichloroborane,phenylbutoxybromoborane, bis(2 chlorovinyl)chloroborane,dibutylchloroborane, dibutylbro-moborane, dimethylbromoborane,diphenylchloroborane, diphenylbromoborane, ethylborane, methylborane,diethylborane, dimethylborane, butylborane, phenylborane,dimethoxyborane.

Preferred boranes are those wherein X, Y and Z are alkyl of 1 through 8carbon atoms, or BH -Q wherein Q is triloweralkylamine.

The polymers of this invention increase the viscosity of organichydrocarbons and are useful as viscosity-increasing oil additives forinternal combustion engines. Some of the polymers can be pressed intotransparent films having adhesive properties and are useful ascomponents of laminated safety glass. The high melting point andstability of the polymers make them useful in applications wheretransparent zfilms are needed to withstand heat.

The foregoing detailed description has been given for clearness ofunderstanding only. The invention is not limited to the exact detailsshown and described, for obvious modifications will occur to thoseskilled in the art.

The embodiments of the invention in which an exclusive property orprivilege is claimed are defined as follows:

1. An imidazole-borane polymer having the recurring structural formulawherein Y and Z are selected from the group consisting of hydrogen,halogen, hydrocarbyl of up to 12 carbon atoms, O-hydrocarbyl of up to 12carbon atoms, substituted hydrocarbyl and O-hydrocarbyl groups in whichthe substituents can be halogen, oxyalkyl, or oxyaryl of up to 6 carbonatoms and wherein Y and Z can be combined to form the divalent groups-O-alkyl-O- and -O- aryl-O- of up to 6 carbon atoms; and wherein R, Rand R are selected from the group consisting of hydrogen, halogen ofatomic number 17-53, alkyl of up to 15 carbon atoms, aryl of 6 throughcarbon atoms, aralkyl of 7 through 12 carbon atoms, alkoxy-carbonyl ofup to 8 carbon atoms, alkoxyalkyl of up to 8 carbon atoms, alkoxy of upto 8 carbon atoms, alkyl-carbonyl of up to 8 carbon atoms, arylcarbonylof up to 12 carbon atoms, alkylthio of up to 8 carbon atoms,aralkyl-thio of up to 12 carbon atoms, cyano, nitro, formyl, ordialkylcarbamido of up to 12 carbon atoms, and wherein R and R can bejoined together to form the group 2. Polymers of claim 1 wherein Y and Zare hydrogen or alkyl of 1 through 8 carbon atoms and R, R and R arehydrogen, alkyl of 1 through 6 carbon atoms, aryl of 6 through 10 carbonatoms, or halogen.

3. The polymer of claim 1 wherein Y and Z are each ethyl and R, R and Rare each hydrogen.

4. The polymer of claim 1 wherein Y and Z are each ethyl, R is methyl,and R and R are each hydrogen.

5. The polymer of claim 1 wherein Y and Z are each ethyl, R is hydrogen,and R and R are joined together to form the group 6. The polymer ofclaim 1 wherein Y, Z, R, R and R are each hydrogen.

7. The polymer of claim 1 wherein Y and Z are each ethyl and R, R and Rare each bromine.

8. Process for preparing polymers of the recurring structure unitwherein Y and Z are selected from the group consisting of hydrogen,halogen, hydrocarbyl of up to 12 carbon atoms, O-hydrocarbyl of up to 12carbon atoms, substituted hydrocarbyl and O-hydrocarbyl groups in whichthe substituents can be halogen, oxyalkyl, or oxyaryl of up to 6 carbonatoms and wherein Y and Z can be combined to form the divalent groups-O-alkyl-O- and -O-aryl-O- of up to 6 carbon atoms; and wherein R, R andR are selected from the group consisting of hydrogen, halogen of atomicnumber 1753, alkyl of up to 15 carbon atoms, aryl of 6 through 10 carbonatoms, aralkyl of 7 through 12 carbon atoms, alkoxycarbonyl of up to 8carbon atoms, alkoxyalkyl of up to 8 carbon atoms, alkoxy of up to 8carbon atoms, alkylcarbonyl of up to 8 carbon atoms, arylcarbonyl of upto 12 carbon atoms, alkylthio of up to 8 carbon atoms, aralkylthio of upto 12 carbon atoms, cyano, nitro, formyl, or dialkylcarbamido of up to12 carbon atoms, and wherein R and R can be joined together to form thegroup wherein R, R and R are defined as above with a reactant of theformula (1) BXYZ wherein Y and Z are defined as above and X is selectedfrom the group consisting of hydrogen, halogen or alkyl up through 8carbon atoms, with the proviso that when Y is hydrogen only one of X andZ can be hydrogen or (2) the compound BXYZ-Q wherein Y and Z are definedas above, X is selected from the group consisting of hydrogen, halogenor alkyl up through 8 carbon atoms, and Q is defined as an electrondonor.

9. The process of claim 8 carried out in the presence of an inertsolvent.

No references cited.

SAMUEL H. BLECH, Primary Examiner.

US. Cl. X.R.

